Multidimensional chromatographic system

ABSTRACT

An on-line multidimensional system which includes a liquid chromatograph having an on-line connection to a pyrolysis probe, which in turn has on-line connection to a gas chromatograph. Preferred applications use a size-exclusion chromatograph coupled to a pyrolysis probe coupled to a gas chromatograph to simultaneously produce composition as a function of molecular weight/size information for polymeric materials.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 07/561,359, nowabandoned, which, in turn, is a continuation of application Ser. No.243,913, filed Sep. 13, 1988, now abandoned.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention generally relates to multidimensionalchromatography, and particularly to an on-line coupled LC/GC systemwhich is capable of generating information for compounds containingnonvolatile components.

Multidimensional chromatography can be a powerful separation tool,especially when dealing with complex matrices which may requireunattainably high theoretical plate counts for adequate resolution.Similarly, multidimensional chromatography has been found quite usefulwhen dealing with samples that require tedious clean-up steps prior toanalysis. The combination of a liquid chromatograph (LC) and a gaschromatograph (GC) in an "on-line" mode has been described in thefollowing references: "On-Line Multidimensional Chromatography UsingPacked Capillary Liquid Chromatography And Capillary GasChromatography", by H. J. Cortes, C. D. Pfeiffer, B. E. Richter, in HRC& CC, 8 (1985) 469., "Determination Of Trace Chlorinated Benzenes InFuel Oil By On-Line Multidimensional Chromatography Using packedCapillary Liquid Chromatography And Capillary Gas Chromatography", by H.J. Cortes, C. D. Pfeiffer, B. E. Richter, D. E. Jensen, in J.Chromatogr., 349 (1985) 55; and "On-Line Multidimensional ChromatographyUsing Micro HPLC-Capillary GC", by H. J. Cortes, C. D. Pfeiffer, inChromatography Forum, 4 (1986) 29. These articles are incorporatedherein by reference.

As discussed in these articles, columns for High Performance LiquidChromatography (HPLC) have been used in an on-line mode primarily forthe determination of trace components in complex matrices, where the LCprovides a highly efficient clean-up step, and a section of thechromatogram containing the components of interest is transferred to aGC for further resolution and quantification. A similar system has alsobeen used to separate components by class, as discussed in "CouplingMicro LC-Capillary GC As A Powerful Tool For The Analysis Of ComplexMixtures", by D. Duquet, C. Dewaele, M. Verzele, in HRC & CC, 11 (1988)252.

Nevertheless, a principal limitation to the use of this LC/GC technologyis the type of compounds that can be analyzed by the GC. In other words,the compounds must be volatile and chromatographable in the gas phase.Nonvolatile or highly polar compounds can be analyzed by a GC if theyare chemically treated (derivatized) to convert them into a moresuitable form. In this regard, see the "Handbook of Derivatives ForChromatography", by K. Blau, and G. King, Heyden & Son, Ltd., London(1978). However, the need to chemically treat these compounds makes itvery difficult to provide an on-line or uninterrupted multidimensionalanalysis of such nonvolatile or highly polar compounds.

Another alternative is the use of pyrolysis gas chromatography toexamine the volatile pyrolysis fragments of a nonvolatile molecule. Inthe characterization of polymers, the combination of size-exclusionchromatography (SEC) and pyrolysis gas chromatography will enable thedetermination of average polymer composition as a function of molecularsize/weight. However, this type of information is difficult to obtain,since fractions eluting from an SEC system are usually collectedmanually, evaporated, redissolved in an appropriate solvent and manuallytransferred to a pyrolysis probe via a syringe.

Accordingly, it is a principal objective of the present invention toprovide a system for coupling liquid and gas chromatography which willpermit on-line multidimensional analysis or determinations ofnonvolatile or highly polar compounds. In this regard, the term"nonvolatile" will be used herein to refer to compounds havingnonvolatile and/or highly polar characteristics.

It is another objective of the present invention to combinesize-exclusion chromatography (SEC) and pyrolysis gas chromatography inan on-line system to permit the determination of the average polymercomposition as a function of molecular size/weight, as well as toprovide valuable information which can be used to understand polymerproperties and polymerization chemistry.

It is a further objective of the present invention to provide an on-linemultidimensional system which is capable of automatically collectingfractions of interest from an SEC and transferring them to an interfacefor permitting GC analysis.

To achieve the foregoing objectives, the present invention provides anon-line multidimensional system which includes a micro size-exclusionchromatograph, and a switching valve for sampling fractions eluting fromthe SEC. The switching valve directly transfers these sampled fractionsto a pyrolysis probe, which produces volatile fragments representativeof the nonvolatile components from the sampled fractions. The systemalso includes a gas chromatograph for providing molecular size/weightdistribution information from the volatile fragments. The presentinvention also enables the combination of the valve, pyrolysis probe andgas chromatograph to be used as an autoinjector when the SEC or other LCis not connected to the system.

The switching valve combines separate sample and solvent flush loops,and causes a carrier fluid to sequentially convey the contents of theseloops to the pyrolysis probe. The pyrolysis probe includes a pyrolysisribbon which is coaxially disposed within a glass housing. The housingfor the pyrolysis probe includes a lateral well portion which directsthe sampled fractions to a confined area of the pyrolysis ribbon. Thepyrolysis probe housing also permits the introduction of an auxiliarycarrier fluid to increase the solvent evaporation rate and minimize theopportunity for the solvent to spread along the pyrolysis ribbon.

Additional advantages and features of the present invention will becomeapparent from a reading of the detailed description of the preferredembodiments which makes reference to the following set of drawings inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an on-line multi-dimensional systemaccording to the present invention.

FIGS. 2A and 2B are diagrammatic views of the load and injectionpositions of the multi-port switching valve shown in FIG. 1.

FIG. 3 is a graph which represents a micro SEC chromatogram of astyrene-actrylonitrile copolymer.

FIG. 4 is a graph which represents a capillary GC chromatogram obtainedfrom the pyrolyzed products of a fraction of the styrene-actrylonitrileshown in FIG. 3.

FIGS. 5A-5D are graphs which represent capillary GC chromatogramsobtained from a polystyrene homopolymer at varying split ratios.

FIGS. 6A-6B are graphs which represent capillary GC chromatogramsobtained from a styrene homopolymer at two different interfacetemperatures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an on-line multi-dimensional chromatographic system10 according to the present invention is shown. The system 10 includes aliquid chromatograph 12, which has a solvent Pump 14, an injection valve16, one or more columns 18 and a detector 20. In one embodimentaccording to the present invention, the solvent pump is an Isco μ -LC500 solvent delivery system (Isco, Lincoln, Nebr., USA), operated at aconstant flow rate. Similarly, the injection valve 16 is a Valco modelNI4W injection valve (Valco Instruments, Houston Tex., USA), with aninjection volume of 200 nl. Additionally, the detector 20 is a JascoUvidec V detector (Jasco International, Japan), which is equipped with amodified cell whose illuminated volume was calculated to be 6 nl fromthe capillary diameter and slit size. A discussion of such a modifiedcell may be found in "Fused Silica Narrow Bore Microparticle PackedColumn HPLC", by F. J. Yang, in J. Chromatogr. 236 (1982) 265. Thisarticle is hereby incorporated by reference.

The columns 18 were constructed of fused silica capillaries with aninternal diameter of 250 μm, (Polymicro Technologies, Phoenix, Ariz.,USA), with a column length of 50 cm. A porous ceramic bed support wasused, as discussed in "Porous Ceramic Bed Supports For Fused SilicaCapillary Columns Used In Liquid Chromatography", by H. J. Cortes, C. D.Pfeiffer, B. R. Richter, and T. S. Stevens, in HRC & CC, 10 (1987) 446.This article is hereby incorporated by reference. The columns 18 werepacked with Zorbax PSM-1000 of 7-μm particle diameter, as a slurry inacetonitrile (5:1), at 6000 psig.

The liquid chromatograph 12 is preferably a micro SEC system, (e.g., forthe characterization of polymers). However, there is no intent to limitthe invention in its broad aspects to a micro system or size exclusionchromatography since the selection of the column dimension and type willbe determined by the sample and information desired. In this regard, amicro SEC system was chosen for the LC 12, because the components ofinterest are diluted in much less volume when compared to a conventionalSEC column. This feature allows the investigation of a polymer inrelatively few analyses. However, if a more detailed examination isdesired, smaller cuts or fractions can be analyzed. Alternatively,microbore or conventional columns could be used. Therefore, the analysiscan provide a larger number of determinations over a narrower molecularsize interval. Since an SEC separates molecules based on size, and thesize of a molecule is related to its molecular weight, the term"molecular size/weight" is used herein to generically refer to molecularsize and/or molecular weight.

The system 10 also includes a multi-port switching valve 22 fortransferring the fractions of interest eluting from the micro SEC 12 toa pyrolysis probe 24. In one embodiment of the present invention, thevalve 22 is a Valco ten port valve model NI10WT. As shown in FIGS. 2Aand 2B this valve was equipped with a 1.0 μl sample loop 26 and a 5.0 μlsolvent flush loop 28. Both of these loops 26-28 were made from 50 μmI.D. silica tubing. A short length of this tubing was also used for theconduit 30 which connects the valve 22 to the pyrolysis probe 24, aswell as the conduit 32 which connects the valve 22 to the detector 20 ofthe micro SEC 12.

FIG. 2A shows the valve 22 in a "load" position, which creates theseparate sample and flush loops. In contrast, FIG. 2B shows the valve 22in an "inject" position, which combines the sample and flush loops. Inthe load position, the effluent from the SEC detector 20 flows throughthe sample loop 26 via the conduit 32. Output flow from the sample loop26 may be stored or transferred to a waste receptacle. Similarly, withthe valve 22 in the load position, a suitable solvent (e.g. THF) willflow through and out of the flush loop 28.

When the valve 22 is switched to the inject position, the sample loop 26will be combined with the flush loop 28, so that the contents of theseloops will be conveyed to the pyrolysis probe 24 by a suitable carrierfluid (e.g., Helium). In addition, another gas such as air can beintroduced to allow cleaning of the system. While other suitableswitching valve arrangements may be used in the appropriate application,the use of a flush loop is preferred because it permits the transferlines from the micro SEC 12 to the pyrolysis probe 24 to be clearedbefore the next sample is collected.

While the preferred valving arrangement is one which first traps apredetermined quantity of the effluent from the SEC 12 in a sample loop,other suitable valving arrangements may be employed in the appropriateapplication. For example, a valve structure could be employed whichchooses between an inject mode and a bypass mode, such that the effluentflow will be passed to the pyrolysis probe, unless the flow is divertedor bypassed to a waste receptacle. Once the effluent flow is diverted,then a carrier fluid may be used to convey the effluent passed throughthe valve to the pyrolysis probe 24.

The pyrolysis probe 24 is generally comprised of a pyrolysis ribbon 34which is coaxially disposed in a glass chamber or housing 36. In oneform of the present invention, the pyrolysis unit used is a HewlettPackard Model 18580A pyroprobe (Hewlett Packard Instruments, AvondalePa., USA), which was operated at 700° C. for one second intervals. Thehousing 36 includes a cylindrical portion 38 through which the pyrolysisribbon 34 extends, and a lateral cylindrical portion 40 which extendsfrom the cylindrical portion in a generally perpendicular direction. Thehousing 36 is also wrapped with a heating tape 41, which is heated atthe appropriate time to approximately 180° C. (outside surfacetemperature).

In accordance with one aspect of the present invention, a depression orwell portion 43 is formed in the pyrolysis ribbon 34 directly beneaththe lateral portion 40 of the housing 36. The well portion 43 in thepyrolysis ribbon 34 is used to receive the individually sampledfractions of interest from the valve 22 via conduit 30. In this regard,the well 43 serves to confine this fluid flow in a specified area of thepyrolysis ribbon 34. Accordingly, the well 43 will cause the transferredfraction to be deposited onto a confined, reproducible area of thepyrolysis ribbon 34.

The inlet port 42 of the lateral portion 40 also permits an auxiliarycarrier gas (e.g., helium, nitrogen or air) to enter the housing 36 viaconduit 44. The flow rate of this auxiliary carrier gas may be adjustedto control the evaporation rate of the solvent transferred into thepyrolysis probe 24. This feature enables the evaporation rate to beincreased, thereby minimizing the opportunity for the solvent and sampleto spread on the pyrolysis ribbon 34.

The housing 36 of the pyrolysis probe 24 also includes an outlet port46, which permits the volatile fragments produced by the pyrolysisribbon 34 to be transferred to a gas chromatograph 48. A short capillarytube 50 extends from the outlet port 46, and fittings 52 are used toconnect the capillary tube to a low dead volume three way tee 54 (SGE,Melbourne, Australia). The tee 54 is used to split the output flow fromthe pyrolysis probe 24. One portion of this flow is directed to thecolumns 56 of the gas chromatograph 48, while the remaining portion isvented through conduit 58. A micro metering valve 60 is connected to theconduit 58 to control the split ratio of vented fluid to GC transferredfluid. Alternatively, a switching valve such as Valco Model N4WT can beplaced between the housing outlet 50, and split tee 54, to allow rapidventing of the solvent.

In one embodiment according to the present invention, the gaschromatograph used is a Varian model 3700 gas chromatograph (VarianAssociates, Walnut Creek, Calif., USA) having a flame ionizationdetector 62. Similarly, the analytical columns 56 were a 50 m×0.20 mmI.D. phenyl-methyl silicone of 0.33 μm film thickness (Hewlett-Packard,Avondale, Pa. USA). The temperature program used was 50° C. for 6minutes, then to 220° C. at 10° or 20° C./min. The temperature programwas initiated at the time of pyrolysis, which preferably took placeafter the solvent eluted from the system. The carrier gas used wasHelium, and the make up gas to the detector 62 was Nitrogen (at 20ml/min.).

Before conducting experiments with the system 10, the SEC columns 18were evaluated and calibrated using narrow distribution anionicpolystyrene standards (Polymer labs, England). Column performance wasestimated by measuring the asymmetry factor, as discussed in"Introduction to Modern Liquid Chromatography", by J. Kirkland, L.Snyder, J. Wiley & Sons, NY (1979). In the case of toluene as thetotally permeated molecule, the asymmetry factor was found to be 1.04,and the column efficiency was found to be 38,000 plates/meter.Resolution was estimated according to the following equation:

    R=D∂=[d log M/dV(ΔV)=d log M,

where D=the slope of the calibration curve, ∂=the standard deviation oftoluene, V=the elution volume, and M=the molecular weight. In theembodiment described, the resolution factor obtained was 0.034.

The elution volume is an SEC system is known to increase with the sampleconcentration due to the change in hydrodynamic volume of a polymer insolution with concentration. In addition, high sample concentrations maycause band broadening due to viscous streaming of the solute band.Accordingly, for the specific polymer and conditions, it is preferredthat the amount of polymer injected into the SEC columns 18 not exceed 2μg in order to achieve accurate molecular weight distributions, as basedupon the calibration procedure discussed above.

The preferred mobile phase solvent used for this specific application,was HPLC grade tetrahydrofuran (Fisher Scientific, Fairlawn, N.J., USA).In this regard, the solvent flow rate was 2.0 μl/min., which yielded acolumn head pressure of 1300 psig. It is known that instrumental flowrate fluctuation can cause large errors in the calculated samplemolecular weight. Accordingly, in order to compensate for any flow ratefluctuations that could be experienced, it is preferred that a smallamount of Toluene be added to the polymer solution being injected inorder to provide an internal standard.

The application of the on-line SEC/pyrolysis GC system 10 to thecharacterization of a stryene-acrylonitrile copolymer is presented inFIGS. 3 and 4. FIG. 3 represents the micro SEC chromatogram obtained onthe polymer prepared by dissolving 10 mg/ml in THF. The variousfractions transferred to the pyrolysis interface 24 are indicated in thechromatogram. FIG. 4 represents the capillary GC chromatogram obtainedafter pyrolysis on the fraction number 1 from FIG. 3 whose molecularweight was between 1,800,000 and 450,000. This GC chromatogram isconsidered typical of the GC chromatograms obtained after pyrolysis ofthe appropriate section across the molecular weight distribution.

The relative composition of copolymer eluted in each fraction wasestimated by measuring the area ratios of the acrylonitrile and styrenepeaks generated. This information is valuable in determining therelative composition as a function of molecular size. In this regard, itwas found that the configuration of the pyrolysis probe has an effect onthe variability of the area ratio data. When pyrolysis takes place, theplatinum ribbon 34 flexes and seldom returns exactly to its originalposition. Accordingly, it is difficult to deposit the fractions ofinterest at the same site of the ribbon as previous fractions, due tothis orientation change. Since the ribbon 34 does not heat evenlythroughout its length, the transferred fractions may experiencedifferent pyrolysis temperatures, and yield variable results. However,as discussed above, the provision of the well 43 in the pyrolysis ribbon34 confines the transferred fractions to a reproducible area, andenables an acceptable standard deviation of the area ratios to beachieved (e.g., 2.4%).

Ideally, the total fraction pyrolyzed should be transferred to the GCcolumns 56. However, it was found that the pyrolysis interface 24 had tobe swept at a high carrier gas flow rate in order to obtain relativelysharp peaks. This situation was also complicated by the fact that the GCcolumns 56 generated relatively high pressures, and therefore resistedthe use of high flow rates from the pyrolysis interface 24. In thisregard, it should be noted that the provision of the split tee 54 wasinstrumental in enabling sufficiently high flow rates to be achieved.Alternatively, the use of wide-bore capillaries may allow rapid transferof the fragmented components to the columns 56 without resorting to asplit ratio system. Alternatively, the function of the split can beaccomplished by replacing it with a cryogenic focusing scheme or a trapsuch as a solid absorbent.

Referring to FIGS. 5A-5D, a series of GC chromatograms are shown toillustrate the experimental effect of various split ratios at the tee 54under the control of the valve 60. For these experiments, the sample wasprepared by dissolving 70 mg of a polystyrene homopolymer in 10 ml ofTHF. A 1.0 μl aliquot of this solution was transferred to the pyrolysisinterface 24 by manually filling the sample loop 26 of the switchingvalve 22 with a syringe for each of the split ratio experiments.Additionally, it should be noted that the columns employed were 50 m×0.2mm I.D. 5% phenylmethyl silicone (df=0.3 μm). The GC oven temperatureprogram used was 50° C. to 240° C. at 10 c/min. The carrier gas used wasHelium at 60 cm/sec., and the makeup carrier gas used was Nitrogen at 20ml/min. The GC detector 62 was set for FID at 320° C., and a split ratiobetween the columns 56 and the detector 62 was varied.

FIG. 5A represents an analysis without any split being employed at thetee 54 (i.e., the total aliquot was transferred to the columns 56 of thegas chromatograph 48). As shown in FIG. 5A, the analysis yielded a highbackground noise level, an overlong solvent peak, and the peak ofinterest (in this case styrene) was broad and split at the top. However,as shown in FIG. 5B, a split ratio of 10:1 resulted in much improvedchromatography. In this respect, it should be understood that the needlevalve 60 was opened such that 10 parts of the fluid flow from thepyrolysis interface 24 would be vented part transferred to the GCcolumns 56. As for FIG. 5C, the split ratio used was 20:1. Similarly,the split ratio used to obtain the chromatogram shown in FIG. 5D was30:1. From these two figures, it should be appreciated that thechromatography was not materially affected, except that the sensitivitywas decreased. Accordingly, a split ratio of 10:1 is preferably employedfor this particular application of multi-dimensional analysis accordingto the present invention.

The temperature of the pyrolysis interface 24 will also have an affecton the chromatography. For example, in classical Pyrolysis GC, theinterface is heated to minimize condensation of the fragments ofinterest and avoid poor chromatography. With respect to themulti-dimensional system 10 according to the present invention, FIGS. 6Aand 6B show the effect of two different pyrolysis interfacetemperatures. Both of these GC chromatograms were obtained bychromatographing the pyrolysis products of a styrene homopolymer, whichwas prepared and deposited onto the pyrolysis ribbon 34 in accordancewith the procedure set forth above for investigating the effect ofvarious split ratios.

FIG. 6A represents the chromatogram obtained at an interface temperatureof 25° C., while FIG. 6B represents the results obtained at an interfacetemperature of 180° C. As shown in these figures, the peak shapesimproved considerably at the higher interface temperature. However, itwas found that when the transfer was made while the interface 24 washeated, the sample tended to splatter and deposit some of the polymer onthe interface walls rather than on the pyrolysis ribbon 34. This yieldedreduced sensitivity and made the reproducibility of the resultsunpredictable. Accordingly, it is preferred that the transfer of thefractions of interest be made at a temperature which does not createexcessive boiling, dependant upon the solvent used. Once the transfer iscompleted, the interface 24 may then be heated to an appropriatetemperature, such as 180° C.

It will be appreciated that the above disclosed embodiment is wellcalculated to achieve the aforementioned objects of the presentinvention. In addition, it is evident that those skilled in the art,once given the benefit of the foregoing disclosure, may now makemodifications of the specific embodiment described herein withoutdeparting from the spirit of the present invention. Such modificationsare to be considered within the scope of the present invention which islimited solely by the scope and spirit of the appended claims.

What is claimed is:
 1. A chromatographic apparatus for providing on-linemultidimensional analysis of a sample containing a nonvolatile componentcomprising:liquid chromatographic means for separating a sample having anonvolatile component into a fraction of interest comprising saidnonvolatile component; pyrolysis means; automatic means for collectingand transferring a fraction of interest eluting from the liquidchromatographic means to the pyrolysis means; gas chromatographic meansarranged for receiving and separating into components at least a portionof the gas effluent of the pyrolysis means; and means for detecting saidfraction of interest after passing through said gas chromatographicmeans to permit the generation of information on said nonvolatilecomponents.
 2. The on-line chromatographic system according to claim 1,wherein said liquid chromatographic means is a size-exclusionchromatograph.
 3. The on-line chromatographic system according to claim2, wherein the size-exclusion chromatographic is a micro size-exclusionchromatograph.
 4. The on-line chromatographic system according to claim3, wherein said transfer means includes valve means for selectivelysampling a predetermined volume of said fractions eluting from saidmicro size-exclusion chromatograph and transferring said sampledfractions to said pyrolysis means.
 5. The on-line chromatographic systemaccording to claim 4, wherein said valve is a switching valve having aninject mode and a bypass mode allowing direct transfer of the liquidchromatographic effluent to the pyrolysis means.
 6. The on-linechromatographic system according to claim 3, wherein said valve means isa multi-port switching valve having a load position and an injectionposition, said load position providing separate sample and flush loops,and said injection position combining said sample and flush loops andcausing a carrier fluid to sequentially convey the contents of saidsample and flush loops to said pyrolysis means.
 7. The on-linechromatographic system according to claim 1, wherein said pyrolysismeans includes a pyrolysis ribbon contained in a housing having inletmeans for receiving said sampled fractions from said liquidchromatographic means and causing said sample fractions to contact saidpyrolysis ribbon, and outlet means for transferring said producedfragments to said gas chromatographic means.
 8. The on-linechromatographic system according to claim 7, wherein said pyrolysisribbon has a depression to confine the transferred section to areproducible area.
 9. The apparatus of claim 8, wherein said pyrolysisribbon is coaxially disposed within the axis of said housing, and saiddepression for said pyrolysis is positioned below a lateral portion ofsaid housing which receives sampled fractions from said valve means. 10.The apparatus of claim 9, wherein said pyrolysis means includes a meansfor heating said housing.
 11. The apparatus of claim 10, wherein saidmeans for heating is a heating tape which is wrapped around saidhousing.
 12. The on-line chromatographic system according to claim 7,wherein said inlet means of said housing also includes a port forreceiving an auxiliary carrier fluid.
 13. The on-line chromatographicsystem according to claim 1, wherein said gas chromatographic meansincludes splitter means for causing one portion of the gas effluent fromsaid pyrolysis means to be vented while causing the remaining portion ofthe gas effluent to be transferred to a column of said gaschromatographic means.
 14. A chromatographic apparatus for providingon-line multi-dimensional analysis of compounds containing nonvolatilecomponents, comprising:a size-exclusion chromatograph; valve means forsampling fractions eluting from said size-exclusion chromatograph, saidvalve means connects a carrier fluid source which causes said sampledfractions to be conveyed from said valve means; a pyrolysis means incommunication with said valve means for producing volatile fragmentswhich are representative of said nonvolatile components from saidsampled fractions; splitter means for receiving gas effluent from saidpyrolysis means while venting a portion of said gas effluent, andtransferring a portion of said gas to gas chromatograph means; and gaschromatograph means for receiving a portion of said fragments from saidpyrolysis means by way of said splitter means for analysis of saidvolatile fragments; and means for detecting said fragments after passingthrough said gas chromatographic means to permit the generation ofinformation on said nonvolatile components.
 15. The apparatus of claim14, wherein said pyrolysis means includes a pyrolysis ribbon containedin a housing having inlet means for receiving said sampled fractionsfrom said size-exclusion chromatographic means, and an outlet means fortransferring said produced fragments to said gas chromatographic means.16. The apparatus of claim 15, wherein said pyrolysis ribbon is providedwith a depression to confine said sampled fractions to a reproduciblearea.
 17. The apparatus of claim 15, wherein said pyrolysis ribbon iscoaxially disposed within said housing, and said depression for saidpyrolysis is positioned below a lateral portion of said housing whichreceives sampled fractions from said valve means.
 18. The apparatus ofclaim 17, wherein said pyrolysis means includes a means for heating saidhousing.
 19. The apparatus of claim 18, wherein said means for heatingis a heating tape which is wrapped around said housing.